There's no indicator on the Pi at all, only a power indicator. But that will stay on as long as the Pi has power. I generally just watch the network activity LED. When it stops blinking/flickering I pull the plug.
You could solder a red LED in serial with a 330 Ω resistor between a GND pin and a GPIO pin. Then you would put a gpioctl() command, for example gpioctl -f /dev/gpioc0 18 1 which would turn the pin 18 to on into /etc/rc.local.
for me as a radio amateur this is a very good solution
I will use the GPIO solution because these ports are protected if I understood the documentation for circiuts in a right way. The serial port is for connection to devices with serial communication.